BPH is characterized pathologically by glandular and stromal hyperplasia leading to nodular expansion of the transition zone (TZ). As many as 50 % of males will require some form of treatment in their lifetime. Screening tests to assess risk for developing symptomatic BPH and tissue or blood based tests to stratify disease severity and to predict treatment response do not exist. BPH is extremely common in the TZ of radical prostatectomies performed for prostate carcinoma. Therefore to screen for candidate biomarkers we will utilize a large bank of snap frozen TZ tissues (> 2000 from > than 500 patients, including MTOPS trial patients) procured intraoperatively during RPs over the last several years. Three parallel screening strategies will be adopted: 1) cDNA microarrays will be used to detect genes that have altered expression correlating with disease severity; 2) TZ tissues implanted in the renal capsule of SCID mice will be used to identify genes regulated by androgens and the nuclear receptor peroxisome proliferator activated receptor gamma (PPAR() in human prostate in vivo by comparing gene expression in tissues from intact or castrated mice with or without treatment with agents such as testosterone, finasteride and ligands for PPARgamma; 3) data base mining will be used to identify candidate genes which can then be studied for altered expression in progressively severe BPH and for allelic variation in blood drawn from BPH patients. The combination of these strategies will allow identification of genes, or groups of genes by more than one approach. Correlation of expression of these genes in samples with progressively severe BPH will be confirmed by real time RT-PCR and epithelial and/or stromal localization of candidate genes will be determined by immunohistochemistry and in situ hybridization. Hormonally modulated genes and those that are involved in regulating epithelial-stromal interactions are likely to be useful markers for disease and/or targets for novel therapeutics. Analysis of the results from these different strategies will indicate candidate genes to investigate for their role in regulating epithelial-stromal interactions in a tissue recombination system allowing for selectively manipulating gene expression in either prostate epithelium or stroma. This integrated interdisciplinary approach involving prostate investigators in Pathology, Urology, and Medical Genetics and key Core facilities at Vanderbilt will facilitate the success for this program. Large volumes of available cases and novel detection strategies will allow for the discovery and characterization of biomarkers useful in managing BPH patients. Models employed will be useful for characterizing the role of novel gene targets identified within the MTOPS Consortium as well as for testing new therapeutic strategies.